来源：https://developer.android.com/reference/android/widget/Button
added in API level 1
Button
public class Button extends TextView
| java.lang.Object | |||
| ↳ | android.view.View | ||
| ↳ | android.widget.TextView | ||
| ↳ | android.widget.Button | ||
| Known direct subclasses |
| Known indirect subclasses |
A user interface element the user can tap or click to perform an action.
To display a button in an activity, add a button to the activity's layout XML file:
<Button android:id="@+id/button_id" android:layout_height="wrap_content" android:layout_width="wrap_content" android:text="@string/self_destruct" />
To specify an action when the button is pressed, set a click listener on the button object in the corresponding activity code:
public class MyActivity extends Activity { protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.content_layout_id); final Button button = findViewById(R.id.button_id); button.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { // Code here executes on main thread after user presses button } }); } }
The above snippet creates an instance of View.OnClickListener and wires the listener to the button usingsetOnClickListener(View.OnClickListener). As a result, the system executes the code you write in onClick(View) after the user presses the button.
The system executes the code in onClick on the main thread. This means your onClick code must execute quickly to avoid delaying your app's response to further user actions. See Keeping Your App Responsive for more details.
Every button is styled using the system's default button background, which is often different from one version of the platform to another. If you are not satisfied with the default button style, you can customize it. For more details and code samples, see the Styling Your Button guide.
For all XML style attributes available on Button see Button Attributes, TextView Attributes, View Attributes. See the Styles and Themes guide to learn how to implement and organize overrides to style-related attributes.
Summary
Inherited XML attributes |
|
|---|---|
| From class |
|
| From class |
|
Inherited constants |
|---|
| From class |
| From class |
Inherited fields |
|---|
| From class |
Public constructors |
|
|---|---|
Button(Context context) Simple constructor to use when creating a button from code. |
|
Button(Context context, AttributeSet attrs)
|
|
Button(Context context, AttributeSet attrs, int defStyleAttr) This constructor allows a Button subclass to use its own class-specific base style from a theme attribute when inflating. |
|
Button(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) This constructor allows a Button subclass to use its own class-specific base style from either a theme attribute or style resource when inflating. |
|
Public methods |
|
|---|---|
CharSequence |
getAccessibilityClassName() Return the class name of this object to be used for accessibility purposes. |
PointerIcon |
onResolvePointerIcon(MotionEvent event, int pointerIndex) Returns the pointer icon for the motion event, or null if it doesn't specify the icon. |
Inherited methods |
|
|---|---|
| From class |
|
| From class |
|
| From class |
|
| From interface |
|
| From interface |
|
| From interface |
|
| From interface |
|
Public constructors
Button
added in API level 1
public Button (Context context)
Simple constructor to use when creating a button from code.
| Parameters | |
|---|---|
context |
Context: The Context the Button is running in, through which it can access the current theme, resources, etc. |
See also:
Button
added in API level 1
public Button (Context context, AttributeSet attrs)
LayoutInflater calls this constructor when inflating a Button from XML. The attributes defined by the current theme'sandroid:buttonStyle override base view attributes. You typically do not call this constructor to create your own button instance in code. However, you must override this constructor when creating custom views.
| Parameters | |
|---|---|
context |
Context: The Context the view is running in, through which it can access the current theme, resources, etc. |
attrs |
AttributeSet: The attributes of the XML Button tag being used to inflate the view. |
See also:
Button
added in API level 1
public Button (Context context, AttributeSet attrs, int defStyleAttr)
This constructor allows a Button subclass to use its own class-specific base style from a theme attribute when inflating. The attributes defined by the current theme's defStyleAttr override base view attributes.
For Button's base view attributes see Button Attributes, TextView Attributes, View Attributes.
| Parameters | |
|---|---|
context |
Context: The Context the Button is running in, through which it can access the current theme, resources, etc. |
attrs |
AttributeSet: The attributes of the XML Button tag that is inflating the view. |
defStyleAttr |
int: The resource identifier of an attribute in the current theme whose value is the the resource id of a style. The specified style’s attribute values serve as default values for the button. Set this parameter to 0 to avoid use of default values. |
See also:
Button
added in API level 21
public Button (Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes)
This constructor allows a Button subclass to use its own class-specific base style from either a theme attribute or style resource when inflating. To see how the final value of a particular attribute is resolved based on your inputs to this constructor, see View.View(Context, AttributeSet, int, int).
| Parameters | |
|---|---|
context |
Context: The Context the Button is running in, through which it can access the current theme, resources, etc. |
attrs |
AttributeSet: The attributes of the XML Button tag that is inflating the view. |
defStyleAttr |
int: The resource identifier of an attribute in the current theme whose value is the the resource id of a style. The specified style’s attribute values serve as default values for the button. Set this parameter to 0 to avoid use of default values. |
defStyleRes |
int: The identifier of a style resource that supplies default values for the button, used only if defStyleAttr is 0 or cannot be found in the theme. Set this parameter to 0 to avoid use of default values. |
See also:
Public methods
getAccessibilityClassName
added in API level 23
public CharSequence getAccessibilityClassName ()
Return the class name of this object to be used for accessibility purposes. Subclasses should only override this if they are implementing something that should be seen as a completely new class of view when used by accessibility, unrelated to the class it is deriving from. This is used to fill in AccessibilityNodeInfo.setClassName.
| Returns | |
|---|---|
CharSequence |
|
onResolvePointerIcon
added in API level 24
public PointerIcon onResolvePointerIcon (MotionEvent event, int pointerIndex)
Returns the pointer icon for the motion event, or null if it doesn't specify the icon. The default implementation does not care the location or event types, but some subclasses may use it (such as WebViews).
| Parameters | |
|---|---|
event |
MotionEvent: The MotionEvent from a mouse |
pointerIndex |
int: The index of the pointer for which to retrieve the PointerIcon. This will be between 0 and MotionEvent.getPointerCount(). |
| Returns | |
|---|---|
PointerIcon |
|